Refractory material with stainless steel and organic fibers

ABSTRACT

A refractory includes a cement, a binder and a matrix. The matrix comprises both stainless steel fibers and organic fibers. The refractory can be easily cast, without additional steel reinforcement, into large fire wall  16  panels  10  capable of meeting the requirements of testing conducted in accordance with ASTM E-119,  Standard Test Methods for Fire Tests of Building Construction and Materials  in support of IEEE Std. 979-1994,  Guide for Substation Fire Protection . The fire wall  16  assembly withstood the fire endurance test without passage of flame and gases hot enough to ignite cotton waste during a four-hour fire exposure. The assembly also withstood a 45 psi water stream for five minutes immediately following the four-hour fire exposure period. This is a stringent mechanical requirement, as all fire walls  16  must maintain their integrity before, during and after a fire, per the Universal Building Code&#39;s definition of a true fire wall  16.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/343,856, filed on Jan. 5, 2012, entitled “REFACTORY MATERIAL WITHSTAINLESS STEEL AND ORGANIC FIBERS,” which is a continuation of U.S.Pat. No. 8,118,925 filed on Aug. 14, 2008, and issued on Feb. 21, 2012entitled “REFACTORY MATERIAL WITH STAINLESS STEEL AND ORGANIC FIBERS,”which in turn claims priority from PCT International Patent ApplicationNo. PCT/US2007/062147, filed on Feb. 14, 2007, entitled “REFRACTORYMATERIAL WITH STAINLESS STEEL AND ORGANIC FIBERS,” which claims priorityfrom U.S. provisional patent application No. 60/773,055, filed Feb. 15,2006, entitled “Removable Fire Walls,” the contents of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates generally to refractory materials and large firewalls made from such refractory materials.

BACKGROUND OF THE INVENTION

Large fire walls, such as fire walls capable of providing protectionagainst fires in oil refineries and large electrical transformers aretraditionally made from ordinary concrete. The problem with fire wallsconstructed from ordinary concrete is that they must be extremely thickto adequately withstand the high temperatures created from largehydrocarbon pool fires with long durations (typically 2000° F. andlasting six hours or more).

Accordingly, there is a need for new materials from which large firewalls can be created which provide sufficient protection against large,very long-lasting and hot fires without requiring excessive thickness tosimultaneously meet severe mechanical requirements.

SUMMARY

The invention satisfies this need. The invention is a refractorycomposition comprising a cement, a binder and a matrix material, whereinthe matrix material comprises both stainless steel fibers and organicfibers. The refractory can be easily cast, without additional steelreinforcement, into large fire wall panels capable of meeting therequirements of testing conducted in accordance with ASTM E-119,Standard Test Methods for Fire Tests of Building Construction andMaterials in support of IEEE Std. 979-1994, Guide for Substation FireProtection. The fire wall assembly withstood the fire endurance testwithout passage of flame and gases hot enough to ignite cotton wasteduring a four-hour fire exposure. The assembly also withstood a 45 psiwater stream for five minutes immediately following the four-hour fireexposure period. This is a stringent mechanical requirement, as all firewalls must maintain their integrity before, during and after a fire, perthe Universal Building Code's definition of a true fire wall.

DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription, appended claims and accompanying drawings where:

FIG. 1 is a side view of a fire wall having features of the invention;

FIG. 2 is a perspective view of a partially completed fire wall havingfeatures of the invention;

FIG. 2A is a cross-sectional view of a vertical beam from FIG. 1,showing the insertion of two walls disposed on opposite sides of thevertical beam;

FIG. 2B is a first alternative cross-sectional view of a vertical beam,showing the insertion of two walls disposed at right angles with oneanother;

FIG. 2C is a second alternative cross-sectional view of a vertical beam,showing the insertion of three walls into the vertical beam;

FIG. 2D is a third alternative cross-sectional view of a vertical beam,showing the insertion of four walls into the vertical beam;

FIG. 3 is a detail plan view of a vertical beam useable in theinvention;

FIG. 4 is a side view showing rebar reinforcement disposed within thevertical beam illustrated in FIG. 3;

FIG. 5 is a front view showing rebar reinforcement disposed within thevertical beam illustrated in FIG. 3;

FIG. 6 is a rebar tying diagram for rebar reinforcement useable in avertical beam within the invention;

FIG. 7 is a plan view of a vertical beam useable in the inventionshowing the vertical beam's attachment to a base plate;

FIG. 8 is a cross-sectional view of the vertical beam illustrated inFIG. 7, taken along line 8-8;

FIG. 9 is a cross-sectional view of the vertical beam illustrated inFIG. 8, taken along line 9-9;

FIG. 10 is a detail view of the attachment of the base plate to rebarreinforcement within the vertical beam illustrated in FIG. 8;

FIG. 11 is a front view illustrating the installation of a vertical beamuseable in the invention to a foundation;

FIG. 12 is a side view illustrating the installation of the verticalbeam illustrated in FIG. 11;

FIG. 13 is a plan view of the vertical beam showing an enclosure for theprotection of its base plate;

FIG. 14 is a cross-sectional view of the vertical beam illustrated inFIG. 13 taken along line 14-14;

FIG. 15 is a side view of the vertical beam illustrated in FIG. 13;

FIG. 16 is a second plan view of a vertical beam having a base plateprotected by a protective enclosure;

FIG. 17 is a cross-sectional view of the vertical beam illustrated inFIG. 16 taken along line 17-17;

FIG. 18 is a front view of the vertical beam illustrated in FIGS. 13 and16;

FIG. 19 is a rear view of the vertical beam illustrated in FIG. 13; and

FIG. 20 is a side view of a stainless steel fiber useable in theinvention.

DETAILED DESCRIPTION

The following discussion describes in detail one embodiment of theinvention and several variations of that embodiment. This discussionshould not be construed, however, as limiting the invention to thoseparticular embodiments. Practitioners skilled in the art will recognizenumerous other embodiments as well.

The invention is a refractory comprising a cement, a binder, water and amatrix material. The matrix material comprises both stainless steelfibers and organic fibers.

The cement can be any suitable cement, such as Portland cement. Thebinder can be any suitable binder, such as calcium silicate or aluminumsilicate.

Where the refractory comprises calcium silicate and Portland cement, thewater content is typically between about 10% and about 15% of thecombined weight of the calcium silicate, Portland cement and water, moretypically between about 11% and about 12%.

In addition to stainless steel fibers and organic fibers, the matrixtypically comprises a variety of other mineral fillers. A typical premixof cement, binder and the non-stainless steel and non-organic portion ofthe matrix contains 40% to 60% (by weight) aluminum oxide, 0% to 20% (byweight) aluminum silicate, up to 30% cement, smaller amounts ofcrestobalite silica and quartz silica, and water.

An exemplar of such typical premix contains 44.5% (by weight) silicondioxide, 34.1% (by weight) aluminum oxide, 16.5% (by weight) calciumoxide, 1.8% (by weight) ferric oxide and 13% water. This exemplar premixis capable of forming a concrete having the following typicalcharacteristics:

Permanent Linear Change % After heating to: 110° C. (230° F.) −0.10 425°C. (800° F.) −0.15 650° C. (1200° F.) −0.30 Density g/cm³ kg/m³ pcfAfter heating to: 110° C. (230° F.) 2.12 2120 132 425° C. (800° F.) 2.102100 131 650° C. (1200° F.) 2.08 2080 130 MPa kg/cm² psi Modulus ofRupture As cured: 8.00 81.58 1160 After heating to: 110° C. (230° F.)8.62 87.91 1250 425° C. (800° F.) 6.55 66.81 950 650° C. (1200° F.) 4.4845.71 650 Cold Crushing Strength As cured:  1 day 31.0 316.46 4500  3days 37.9 386.78 5500  7 days 39.3 400.84 5700 28 days 50.0 499.30 7100Thermal Conductivity W/m° K BTU-in/hr-ft²-° F. (Hot Wire Method ASTMC-1113) After heating to: 100° C. (210° F.) 1.17 8.11 250° C. (480° F.)1.15 7.97 450° C. (840° F.) 1.26 8.74 600° C. (1110° F.) 1.27 8.81Coefficient of Thermal Expansion From 110° F.-1600° F. 3.75 × 10⁻⁶/° F.From 38° C.-871° C. 6.72 × 10⁻⁶/° C.

In the matrix, stainless steel is used instead of ordinary steel becauseof stainless steel's higher temperature resistance, higher strength,non-corrosion characteristics and non-magnetic properties.

The stainless steel fibers can be 304 type stainless steel fibers. Othertypes of stainless steel from the 300 Series can also be used to makethe fibers, such as: 301, 302, 303, 309, 316, 321 and 347. Typically,the weight percentage of the stainless steel fibers within the dryrefractory mix (before water is added) is between about 1.2% and about1.6% (by weight) of the dry refractory mix.

The stainless steel fibers are preferably corrugated to increase theeffective surface area of the fibers and to facilitate their bonding andattachment within the matrix. In one embodiment of the invention, thestainless steel fibers each have a length of about one inch, a width ofabout 0.045 inch and a thickness of about 0.02 inches. These exemplarystainless steel fibers are corrugated such as the stainless steel fiber2 illustrated in FIG. 20. Each stainless steel particle 2 has a basesection 4 having a length of about 0.18 inch, followed by ninealternating positive and negative corrugations 6. Each corrugation 6 hasa height h of about 0.0075 inch and a length l of about 0.08 inch long.After the series of nine corrugations, the particle terminates with asecond, oppositely disposed base section 8 having a length of about 0.1inch. Such stainless steel fibers can be purchased from FiberconInternational of Evans City, Pa.

The organic fibers are important in the refractory to provide minutechannels (upon melting during a fire) to facilitate gas venting withoutfracturing the refractory. These fibers also mitigate crack formationduring curing.

The organic fibers can comprise polypropylene fibers, preferably inexcess of 90% polypropylene fibers. Typically, at least about 90% of theorganic fibers have a length between about 0.2 inch and about 0.3 inchand a diameter between about 0.001 inch and about 0.002 inch.

The organic fibers are typically about 1% by weight of the dryrefractory mix. The fibers have a variety of shapes and are notnecessarily linear. The length of each of the organic fibers is mosttypically 0.25 inches. Typically, the fibers have a relatively constantcircular cross-section with a diameter between about 0.001 and about0.004 inches. In a typical embodiment of the invention, smaller diameterorganic fibers greatly outnumber larger diameter organic fibers, forexample by at least a ratio of 50:1. Such organic fibers can bepurchased from Allied Mineral of Columbus, Ohio.

Both the stainless steel fibers and the organic fibers are randomlyoriented within the refractory.

Refractory panels 10 can be conveniently cast from the refractory of theinvention. Cure time for even very large panels 10 is as little as 12hours at ambient temperatures. Kiln drying is not required.

A typical refractory of the invention has the following characteristics:

1. Mechanical Properties at Ambient Temperature:

a. Specific gravity: 134 pcf

b. Modulus of elasticity, E, ksi:

-   -   2,500-5,000 Unreinforced (UR);    -   15,000-25,000 Steel Reinforced (SR)

c. Shear Strength, F_(v), ksi (reported as Modulus of Rupture forceramics and refractories):

-   -   1.1 (UR);    -   14.4 (SR)

d. Bending Strength F_(b), ksi:

-   -   Not applicable for UR matrix;    -   34.8 (SR)

e. Tension and compress strength, F_(t) and Fc ksi:

-   -   5.25 (UR—compression; F_(t)<290 psi, hence not usually used for        characterizing inelastic materials); 52 tension and 48        compression (SR)

2. Electrical Conductivity and Other Electrical Properties (UR):

Dielectric strength=90 v/mil; Dielectric constant about 5;

Resistivity=52×10¹⁰ ohm-cm

3. Thermal Properties:

a. Thermal conductivity (Hot Wire Method ASTM C-1113)

After heating to Btu-in/hr-ft²-° F.  400° F. 4.20 8000° F. 4.41 1200° F.4.69 1825° F. 4.90

b. Thermal expansion coefficient

From 100° F. to 2000° F. 3.75 × 10⁻⁶/° F. From 38° C. to 1093° C. 6.72 ×10⁻⁶/° C.

c. Fire rating requirement

-   -   1,205° C. working temperature

d. Mechanical strength at high temperatures:

MPa kg/cm² psi Modulus of Rupture (unreinforced) As cured: 7.58 77.361100 After heating to:  110° C. (230° F.) 8.27 84.39 1200  540° C.(1000° F.) 4.48 45.71 650 1205° C. (2200° F.) 7.58 77.36 1100 ColdCrushing Strength (unreinforced) As cured:  1 day 36.20 369.2 5250  3days 39.92 407.2 5790  7 days 39.78 405.8 5770 28 days 39.30 400.0 5700After heating to:  110° C. (230° F.) 38.61 393.8 5600  540° C. (1000°F.) 29.17 297.5 4230 1205° C. (2200° F.) 38.27 390.3 5550

The refractory composition of the invention can be conveniently castinto an infinite variety of shapes. For example, the refractorycomposition of the invention can be cast into large panels 10 suitablefor use in constructing a high temperature fire walls. Such large panels10 are typically between about 5 feet and about 10 feet in length,between about 2 feet and about 5 feet in width and between about 1 inchand about 3 inches in thickness. Such panels 10 typically weigh betweenabout 400 pounds and about 800 pounds.

The refractory of the invention can be conveniently mixed within anordinary cement mixer. After adequate mixing of all of the ingredients,the wet mixture can then be poured into molds. The molds are preferablygently vibrated to eliminate air pockets and to evenly distribute thestainless steel fibers.

Surprisingly, even such large panels 10 do not require additional steelreinforcement within the panel, such as steel frameworks and rebarcages. In fact, the use of such additional steel reinforcement has beenfound in many cases to be detrimental to the integrity of the panel 10when subjected to high heat followed by a rapid cool down. Cracking canoccur during cool down of panels 10 having additional steelreinforcement due to the disparity in coefficients of expansion betweenthe additional steel reinforcement and the refractory composition.

Fire walls 16 made with such large panels 10 can comprise a plurality ofpanels 10 disposed between vertical beams 12, such as illustrated inFIGS. 1 and 2. Both the panels 10 and the vertical beams 12 can be castfrom the refractory of the invention.

The vertical beams 12 weigh typically in excess of 5000 pounds. Eachvertical beam 12 preferably comprises a slot 14 into which a pluralityof panels 10 can be stacked one on top of the other to form fire walls16 of various shapes (see FIGS. 2A-2B and 3).

Unlike panels 10 cast from the refractory of the invention, verticalbeams 12 cast from the refractory are typically reinforced with rebarcages 18 in the same manner as ordinary concrete beams are reinforcedwith rebar cages (see FIGS. 4, 5, 6, 8 and 9).

The vertical beams 12 typically are attached to a traditional concretefoundation 20 using a base plate 22 which is welded to steelreinforcement bars 24 disposed within the vertical beams 12 (see FIG.10). The base plate 22 is made of steel and attached to the foundationusing steel bolts 26, and so must be protected in the event of a fire.Such protection can be provided by installing a base plate cover 28 madefrom the refractory of the invention around each of the base plates 22(see FIGS. 13-17).

Alternatively, the vertical beams 12 can be standard I beams or H beams(not shown) which have been clad with the refractory of the invention.

An optional door (not shown) can be created within the fire wall 16.Such a door can be used for access by maintenance personnel. The doorcan be made of short panels of the present refractory and can be made toslide into a door frame. Typically, the door is located next to avertical beam 12 with hinges for the door attached to the beam 12.

Such modular fire walls 16 provide easy assembly and disassembly at thesite and are completely removable. The modular characteristics of thefire wall 16 simplify specification, assembly and disassembly, andminimize manufacturing and insulation costs without compromising thermalor mechanical performance.

Large fire walls 16 of the invention have been found to comply with thestandards for a four-hour rating under ASTM E-119 as previously stated.

The refractory of the invention provides many advantages over mostrefractories of the prior art. The invention provides a high-strengthrefractory having excellent fire resistance. Expansion and contractionbetween temperatures below freezing and temperatures in excess of 900°C. are relatively small. The refractory is corrosion, mold, rot andinfestation resistance. It is impermeable to moisture, to air and toother gases. Cracking during curing is minimal, as is cracking duringinitial temperature increases (up to about 150° C.) and when subject tohigh temperatures (temperatures higher than 150° C.). The refractory hasthe built-in ability to relieve trapped gases at medium and hightemperatures. The refractory can be fully cured at ambient temperatureand pressure.

Having thus described the invention, it should be apparent that numerousstructural modifications and adaptations may be resorted to withoutdeparting from the scope and fair meaning of the present invention.

1. A fire wall cast from a refractory composition, the refractorycomposition comprising: (a) a cement; (b) a binder; and (c) a matrixmaterial comprising stainless steel fibers and organic fibers, and arefractory aggregate comprising aluminum oxide, calcium oxide, ironoxide and silicon dioxide or a combination thereof.
 2. The fire wall ofclaim 1 comprising a plurality of panels disposed between verticalbeams, both the panels and the vertical beams being cast from arefractory composition, wherein the panels contain no additional steelreinforcement.
 3. The fire wall of claim 2, wherein the panels have apair of opposed end edges, and wherein the vertical beams comprise agroove into which an end edge of each panel is disposed.
 4. The firewall of claim 1, wherein the fire wall is cured at ambient temperature.5. The fire wall of claim 2, further comprising a steel base plate. 6.The fire wall of claim 5, wherein the steel base plate is continuousacross one or more panels and vertical beams.
 7. The fire wall of claim5, wherein the steel base plate is encapsulated by a box cast from arefractory composition.
 8. The fire wall of claim 2, wherein the one ormore panels maintain impact strength of at least 45 pounds per squareinch at about 2000° F.
 9. The fire wall of claim 2, wherein the one ormore panels are corrosion, rot, and erosion resistant.
 10. The fire wallof claim 7, wherein the panels are cured at ambient temperature.
 11. Apanel for use in a firewall, the panel cast from a refractorycomposition, the refractory composition comprising: (a) a cement; (b) abinder; and (c) a matrix material comprising stainless steel fibers andorganic fibers, and a refractory aggregate comprising aluminum oxide,calcium oxide, iron oxide and silicon dioxide or a combination thereof.12. The panel of claim 11, further comprising an opening.
 13. The panelof claim 12, wherein the opening is reinforced.
 14. The panel of claim11, further comprising a door.
 15. The panel of claim 14, wherein thedoor is supported by hinges.
 16. The panel of claim 14, wherein the dooris hung from the top of the panel.